So called boat leveling devices of the trim tab type have been known for many years and various forms of them have been developed in an effort to maximize attitude control, stability of the marine craft and general hydrodynamic efficiency inclusive of decrease of flow velocity under the hull and fuel efficiency.
The prior art trim tabs are typically provided in pairs to enhance stability of the craft, which are attached directly to the transom of a watercraft and in which the attitude of the trim tab is controlled through a hydraulic piston assembly which controls relative angulation of the whole relative to level of the water.
In general trim tabs of the prior art, whether double or single acting, will operate upon the same principles and have a common objective, namely, that of contributing to the efficiency control of the boats attitude, stabilization and general hydrodynamics.
In recent years, most efforts of the prior art have been directed primary to improvement of the electronics in the development of algorithms to optimize trim tab control under various conditions of speed, shape of the boat's hull, having distribution in craft, and other hydrodynamic considerations. The prior art also has experimented with the efficiency of electric motor controls of the trim tab as opposed to that of the hydraulic systems.
The U.S. Navy has undertaken significant research and development in this area to attempt to maximize performance of a variety of its boats and, typically, of the types employed by the U.S. Coast Guard. In Navy terminology, a trim-tab is referred to as a stern flap, apparently because its engineering objectives are more ambitious than are the case with a leisure class powerboat. More particularly, the Navy has identified the following criteria as hydrodynamic mechanisms which account for improved boat performance based on optimized stern flap design.
After Body Flow Modifications:
Flow velocity under the hull decreased.
Pressure recovery increased.
Transom exit velocity increased.
Wave System Modifications:
Localized transom system wave system altered.
Near field wave heights reduced.
Far field wave energy reduced.
Secondary Stern Flap Hydrodynamic Effects:
Ship length increased.
Beneficial propulsion interactions.
Ship trim modified (bow down trim induced).
Ship sinkage reduced.
Lift and drag forces developed on flap.
The most common material used in trim tab design is stainless steel, but materials can vary between stainless steel, aluminum, bronze, brass, carbon fiber, fiberglass, or other material known to be used in trim tab design.
The within inventor has recognized that the fundamental objectives and benefits of trim tabs and stern flaps may be more effectively achieved if the entire chord length of the trim-tabs or stern flaps are extended. And that, when properly actuated and controlled, such elongated attitude control element, as suggested can accomplish and substantially improve upon the performance of prior art trim tabs and stern flaps regardless of hydrodynamic conditions. The efficiency of the present invention may be yet further improved by the assistance of contemporary electronic controls and algorithms. The present invention also improves upon efforts that seek to improve the performance of trim-tabs thereof through modifications of their geometry as, for example, is reflected in U.S. Design Pat. No. 292,392 (1987) to Zepp, entitled Boat Leveler Twin Tab and the prior art of Karafiath et al. U.S. Pat. No. 9,180,933 B1 (2015), and Cusanelli U.S. Pat. No. 6,698,370 B1 (2004).
While this use of trim tabs has been shown to help attitude control and stability, there exists a need for a method of optimizing trim-tab surface area to increase the efficiency of watercrafts, and use of an adaptable design that can alter the degree of the trim tab based on certain speeds.